In co-pending patent application Ser. No. 748,759, by Berde, et al., and assigned to the present assignee, an audio signal may be inserted into a composite video signal by synchronizing three evenly spaced samples of the audio signal with each horizontal sync pulse in the video signal. Insertion of the three audio samples at the end of each horizontal line in the video signal is accomplished by first converting the audio samples to red, green and blue video samples. Since the converted audio samples are inserted only at the end of each video horizontal line, the "picture" portion of the video is unaffected by such addition of a second audio channel.